[COOP] access reporting: access-to-other test.

Add a basic WPT test where the reported: body.type is:
"access-from-coop-page-to-other"

This is very similar to the previous tests about
"access-to-coop-page-from-other" added in:
https://chromium-review.googlesource.com/c/chromium/src/+/2367098

Bug: 1090273
Change-Id: I3b558ed91cbeb48a47d700b9ade0dd9be612962b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2374529Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#802146}

third_party/blink/web_tests/external/wpt/html/cross-origin-opener-policy/reporting/access-reporting/access-from-coop-page-to-other_coop-ro.https.html

+<title>
+  One window accesses a second one. They are aren't related by an opener/openee
+  relationship. The first window has set
+  Cross-Origin-Opener-Policy-Report-Only:same-origin, so it receives a
+  "access-from-coop-page-to-other" report.
+</title>
+<meta name=timeout content=long>
+<script src=/resources/testharness.js></script>
+<script src=/resources/testharnessreport.js></script>
+<script src=/common/get-host-info.sub.js></script>
+<script src="/common/utils.js"></script>
+<script src="../resources/dispatcher.js"></script>
+<script src="../resources/try-access.js"></script>
+<script>
+
+const directory = "/html/cross-origin-opener-policy/reporting";
+const executor_path = directory + "/resources/executor.html?pipe=";
+const same_origin = get_host_info().HTTPS_ORIGIN;
+const coep_header = '|header(Cross-Origin-Embedder-Policy,require-corp)';
+
+let escapeComma = url => url.replace(/,/g, '\\,');
+
+promise_test(async t => {
+  const report_token= token();
+  const report_to = reportToHeaders(report_token);
+
+  // The test window.
+  const this_window_token = token();
+
+  // The "opener" window. With COOP:same-origin + reporter.
+  const opener_token = token();
+  const opener_url = same_origin + executor_path + report_to.header +
+    report_to.coopReportOnlySameOriginHeader + coep_header +
+    `&uuid=${opener_token}`;
+
+  // The "openee" window. With COOP:same-origin + reporter.
+  const openee_token = token();
+  const openee_url = same_origin + executor_path + report_to.header +
+    report_to.coopReportOnlySameOriginHeader + coep_header +
+    `&uuid=${openee_token}`;
+
+  // The "other" window.
+  const other_token = token();
+  const other_url = same_origin + executor_path + report_to.header +
+    `&uuid=${other_token}`;
+
+  t.add_cleanup(() => {
+    send(opener_token, "window.close()")
+    send(openee_token, "window.close()")
+    send(other_token, "window.close()")
+  })
+
+  // 1. Create the "opener" window.
+  let opener_window_proxy = window.open(opener_url);
+
+  // 2. Create the "openee" window.
+  send(opener_token, `
+    window.openee = window.open('${escapeComma(openee_url)}');
+  `);
+
+  // 3. Create the "other" window.
+  send(openee_token, `
+    window.other = window.open('${escapeComma(other_url)}');
+  `);
+
+  // 4. Wait for "other" to load its document.
+  send(other_token, `send('${this_window_token}', "Loaded");`);
+  assert_equals(await receive(this_window_token), "Loaded");
+
+  // 5. "opener" accesses "other" window, through "openee".
+  send(opener_token, `
+    tryAccess(openee.other);
+  `);
+
+  // 6. Check a report is sent to the openee.
+  let report =
+    await receiveReport(report_token, "access-from-coop-page-to-other")
+  assert_not_equals(report, "timeout", "Report not received");
+  assert_equals(report.type, "coop");
+  assert_equals(report.url, opener_url.replace(/"/g, '%22'));
+  assert_equals(report.body.disposition, "reporting");
+  assert_equals(report.body.effectivePolicy, "same-origin-plus-coep");
+  assert_equals(report.body.property, "blur");
+  assert_source_location_found(report);
+}, "access-from-coop-page-to-other (COOP-RO)");
+
+</script>